1. Field of the Invention
The present invention lies in the field of determining and optimising machining steps for manufacturing sheet-metal forming parts, for example by way of deep-drawing and stretch-forming processes. It relates to a method, a data processing system, a computer program and a data carrier for the computer-aided generation of tool parameters for physical tools for manufacturing sheet-metal forming parts by way of forming processes, according to the respective independent patent claims.
2. Description of Related Art
Sheet-metal forming parts as a rule are manufactured by deep-drawing/stretch-forming. The semi-finished product, the so-called sheet metal billets (or just “billets”), for this purpose, is applied in multi-part forming tools. The parts are shaped by way of presses, in which the shaping tools are clamped. As a rule, the parts are manufactured from a flat sheet-metal billet over several forming stages by way of machining steps or manufacturing steps such as drawing, restriking, forming down, etc., combined with cutting steps.
With the development of the method plan, several forming operations and their contents, which is to say that which is shaped or cut in which operation, as well as descriptions of the physical tools which are required for the manufacture of this part, are determined. Thereby, one proceeds from the finished, constructed part, and nowadays, the procedure is usually as follows.
There are approaches with a differing degree of detailing:    The coarse method is often at the beginning of the planning process, for example in order to have a basis for the calculation of an offer. Here, the operational sequence is fixed, i.e. for each operation, one determines which part regions are machined in which manner. The “auxiliary conditions” such as e.g. the press, are usually not yet known at this point in time.    The fine method arises at a significantly later point in time than the coarse method. This turns out to be much more detailed than the coarse method, on account of the larger “information basis” which is then available. It, thus, comprises e.g. the exact sectional contour for the billet sections, particularities of the drawing operation (draw beads etc.), the pivot position in each operation, and precise working directions of the cams. It serves as an input for the tool design.
Until now, experience has played a large role with the manual production by a human method planner; the evaluation of the method is effected mostly be way of already created methods for parts of the same type, either indirectly by way of the re-use of the obtained knowledge, or directly by way of modifying an already existing method for a similar part. In the course of time, the method planner “learns”:    with which sequences of machining steps one may realise certain part geometries, such as e.g. L-flanges or Z-flanges;    which “combination” of part regions and machining steps may be realized in an operation or should be preferably manufactured together in an operation (e.g. with a side wall, “the folding of the roof channel” and “folding the A-column at the top” may often be easily realized in one operation);    which “combination” of part regions and machining steps may not be realized or only poorly realized in one operation (e.g. with a side wall, the “postforming of the roof channel” and the “postforming of the A-column at the top” may often not be combined together in one operation, since there is not enough space for all cams).
As a rule, uses 2D-screenshots of the part for the visual representation of the coarse method, wherein the methods are then mostly set up with the help of simple guidelines, such as for example    there is a picture for each operation    there is a colour for each processing part (cutting, folding, . . . )
Then the part regions machined in the respective operation are marked with the respective colours. There are also variations with only one picture, in which each colour then corresponds to one operation.
This procedural manner on creating the coarse method entails many disadvantages:    The planner, with each new part, starts from “the very beginning” and constructs the method from scratch again; even when using old method plans, one needs to check for each step, as to whether it may be transferred to the new part or tool without further ado, and the method for the new part is created afresh by hand. This renders the procedure unnecessarily time-consuming and expensive.    Since the found solutions are based to a considerable extent on the experience of the respective planner, to some part they are very difficult to understand by other persons.    The comparability and re-usability of different solutions suffers from the different approach methods of the individual planners, and the absence of company-specific standards.    The insufficient use of 3D-geometry leads to avoidable inaccuracies and the method being prone to error because of this; it may occur that potential problem locations in the geometry are overlooked, and parameters are estimated which could also be computed in an accurate manner (such as e.g. the pivot position).    If no 3D-geometry is used, then there neither exists the possibility of securing the method plan via a simulation.    There are no standardised documents for the communication of the method to suppliers or to customers.
First, cost estimates for the tool investment costs and also offer calculations arise on the basis of the coarse method. Here too, the experience of the human calculator plays an important role, in particular with regard to the estimation of cost, which is why similar problems may be identified as with the creation of the coarse methods:    The calculations may not be reproduced; different calculators arrive at different results, and even the same calculator may arrive at two different results for one and the same tool, since the calculation is subject to his personal assessment.    The calculator begins “from scratch” with each cost calculation.    The poor comparability of the coarse methods, even in combination with the subjective assessment by the calculator, entails a high planning risk: it is not possible to assess and compare different methods and their costs according to objective yardsticks, in order to select the best one.    Often one may not even fall back on different (subjective) methods and their assessments as a planning aid, since the creation and calculation is much too time-consuming. In particular with regard to the suppliers who must provide an offer for one or also more sets of tools within a short time period, time is a very critical factor (partly the time is so limited that it is not even sufficient for the creation of a single method (according to the previous method); and the price offer is then, for example, ascertained by way of each planner or calculator mentioning a number which appears appropriate to him, and taking an average from this).    The calculation of the supplier is not adequately transparent to the client, and changes in the calculations as a rule are not understood.
For the calculation of an offer, it is too much effort to create a representation of the required machining steps and machining tools, which is much more detailed compared to the coarse method, or even create a complete method plan, and to estimate the costs from this.